The technology disclosed herein generally relates to flight management systems for airplanes and, more particularly, relates to techniques for computing predicted flight profile and associated trip prediction parameters in a flight management system.
A flight management system (FMS) installed in the flight deck of a modern airplane performs various flight critical functions such as navigation, guidance, flight planning, datalink and performance. For the performance function, the flight management system has various internal algorithms that utilize aerodynamic and propulsion performance data (hereinafter “baseline performance data”) stored in a baseline performance database to compute predicted flight profile and the associated trip prediction parameters such as estimated time of arrival and predicted fuel consumption quantity. However, the airplane characteristics may vary over time due to small but incremental changes to the airplane aerodynamic and propulsion performance. As a result, the FMS performance algorithms and the baseline performance data may deviate from the actual airplane performance over time as the airplane continues to operate in service. This results in the flight management system computing inaccurate trip prediction
Due to the variability of some airplane characteristics, some airlines may take one or more of the following steps: (1) download and analyze recorded real-time flight data such as fuel flow, speed, altitude, etc. after each flight; (2) try to understand the actual performance and behavior of individual airplane to gain efficiency, detect anomalies and reduce operating costs; and (3) compute fuel flow or drag corrections based on the analysis of the historical flight data and apply those corrections to the baseline FMS performance data by entering them into the flight management system manually as a maintenance task. A most efficient way could be to load a set of correction data tables into the flight management system via datalink and/or as supplemental databases. In the latter case, a new database may need to be created and uploaded to the flight management system as often as needed (weekly or monthly basis). This would entail the expenditure of significant time and effort to update and recertify the new database and/or the flight management system.
Even if the changes to airplane characteristics such as fuel flow and drag were loaded into the flight management system, many FMS performance algorithms would continue to utilize data tables in the baseline performance data, whose values have already been preprocessed using the baseline airplane performance data and are not affected by the corrections loaded to the flight management system, for one or more of the following reasons: (1) due to significant time and effort required to update and recertify the baseline performance data tables, those tables are not modifiable within the flight management system and the airplane continues its operation with the initial certified data that was installed when the airplane was first delivered; (2) even when the updated airplane characteristics data such as fuel flow and drag are available, the flight management system cannot constantly access them to compute the performance parameters due to limited FMS computing power and/or strict FMS timing requirements; and (3) the inputs and outputs of the baseline performance data tables may not be compatible with the updated airplane characteristics data, such as fuel flow and drag.
It would be advantageous to provide a flight management system that is configured to efficiently provide real-time airplane performance calculations for use in computing predicted flight profile and associated trip prediction parameters.